Oracle Database Discussions

I am attempting to access oracle on a home LAN. I can ping the machine which hosts the database (10.1.1.3), but any attempt to make a database connection from my local host (10.1.1.0) has failed. SQL developer reports "the network adapter could not establish a test connection". I'm accessing the server's oracle listener port (1521). Google chrome can't open "//localserver:5500/em" either. I have set up instant client on the local host.

environment variables (localhost is 10.1.1.0)

ORACLE_HOME = F:\app\Roger\product\11.2.0\client_1
ORACLE_SID = orcl

tnsnames.ora on local host

<data source alias> =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.1.1.3)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = orcl)
)
)

I can map network drives on the oracle server (10.1.1.3) from the local host and all machines on the LAN can access the internet through the gateway on the proxy server (10.1.1.1). Of course Oracle is fully functional on 10.1.1.3 itself.

Is a firewall blocking access or is there something else preventing database access from my localhost? The local host has XP service pack 2. The proxy server has Norton antivirus installed, but I don't think I use the gateway for anything other than internet access. The local host has spyware doctor installed, but I still have problems even if I disable the spyware service. I'm getting the impression Oracle is far easier to administer on any operating system other than windows.

Any suggestions appreciated.

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basic LAN config (all machines run windows XP):

local host machine
static IP = 10.1.1.0
-----------------------------------------
Proxy internet server machine

static gateway IP = 10.1.1.1 (LAN card 1)
Internet IP is dynamic and is shared. (LAN card 2)
-----------------------------------------
Oracle server machine

static IP = 10.1.1.3

The DNS for all static addresses is 192.168.0.1